The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
Transdermal delivery is a feasible alternative route of drug administration for many drugs. Drugs whose daily dose is 20-30 mg or less, are potential candidates for transdermal drug delivery (Guy and Hadgraft 1987, Guy and Hadgraft 1989).
Transdermal administration of therapeutically active agents is usually accomplished by incorporating the drug into a transdermal delivery device which is able to control the delivery rate of the drug. According to one alternative the transdermal device comprises a backing layer, an adhesive layer and a matrix layer preferably made of a polymer material in which the drug is dispersed. The rate of which the drug is released from the device is here controlled by the polymer matrix. Another kind of transdermal device is the reservoir system comprising a) a drug impermeable backing layer, b) an adhesive layer, c) a drug permeable membrane sealed to one side of the backing layer as to define a drug reservoir compartment there between, and d) a drug or composition thereof within said drug reservoir. In this case the drug in the reservoir is usually in liquid or gel form. The drug permeable membrane controls the rate at which the drug is delivered to the skin.
U.S. Pat. No. 4,692,462 describes a composition and method for controlled transdermal delivery based on the use of a ion exchange resin loaded with the drug to be administered. This drug-loaded ion exchange resin is, together with a salt that is able to release the drug from the ion exchange resin, mixed with a gel-forming vehicle and incorporated in a device having a cavity, an adhesive layer and a backing layer.